Comparing Static and Dynamic Decision Tasks Using Pupillometry: Expected Loss is More Important than Defined Reward

We report on two experiments using pupillometry to explore decision-making. In Experiment 1, participants observed a static image of the game. In Experiment 2, participants interacted with a computer agent in a cooperative game. A Tobii Pro Fusion running at 120Hz tracked participants’ eyes. Ten participants completed nine trials in each experiment. Percentage change in pupil diameter from a baseline, in Experiment 1, is similar for both targets, suggesting that participants treat low and high rewards equally. In experiment 2, there is also little change in pupil diameter when participants select low-value targets. But when the participant chooses high-reward and the computer chooses a low reward, pupil diameter is affected. This suggests that when participants expect a high reward, but the computer does not cooperate, this is experienced as loss and pupil diameter increases. Loss is more important than reward (as Prospect Theory proposes) and relates to viewing opponent’s actions.